1. Field of the Invention
The present invention relates to a dry etching device and dry etching method, and particularly to an inductively coupled plasma dry etching device and dry etching method.
2. Description of the Related Art
In processing wafers in a semiconductor fabrication process, a dry etching process is carried out in which etching is performed using active gas plasma under reduced pressure to remove only a prescribed thickness of a prescribed area of a thin film formed on a wafer, one type of dry etching device that is used being an inductively coupled plasma (ICP) dry etching device. An inductively coupled plasma dry etching device is a plasma etching device that uses a plasma created by accelerating electrons in an induction field that is brought about by a high-frequency induced magnetic field. The shape of the inductively coupled plasma may be a spiral coil or a coil on flat plate.
FIG. 1A is an overall schematic sectional view of an inductively coupled plasma dry etching device of the prior art, and FIG. 1B is a sectional view of the dome. An inductively coupled plasma dry etching device of the prior art includes etching chamber 110 that houses wafer 130 that is to undergo the etching process, and ceramic dome 120 that is connected to the opening of etching chamber 110 and that is provided for generating plasma within the device. Etching chamber 110 can be maintained in an airtight state while coupled with dome 120.
Etching chamber 110 is provided with gate 111 for inserting and removing wafer 130 and gas injection port 112 for introducing the etching gas. In addition, ESC (electrostatic chuck) stage 131 made of ceramic for securing wafer 130 is provided inside etching chamber 110, while outside etching chamber 110, pressure gauge 113 and pressure controller 140 for regulating gas pressure inside the chamber and discharging gas are connected, and first high-frequency power supply 123 for supplying high-frequency current is connected to ESC stage 131.
Coil 121 is arranged in a helical form on the outside of dome 120, and coil 121 is connected to second high-frequency power supply 124.
Next, regarding the etching method that uses the inductively coupled plasma dry etching device of the prior art, wafer 130 is conveyed by way of gate 111 of etching chamber 110 onto ceramic ESC stage 131, which has the function of securing the wafer. Etching gas is directed at wafer 130, which is secured on ceramic ESC stage 131, from gas injection port 112 directly over wafer 130. The pressure inside etching chamber 110 is detected by gauge 113, and the interior of etching chamber 110 is controlled to a prescribed pressure by linking this detected pressure with an orifice of pressure controller 140, which serves as an exhaust gas outlet, and varying the orifice.
High-frequency power of 13.56 MHz is applied from second high-frequency power supply 124 to coil 121, which is arranged on the exterior surface of ceramic dome 120, high-frequency power of 13.56 MHz is next applied from first high-frequency power supply 123 to ceramic ESC stage 131, and the etching gas inside etching chamber 110 is excited to generate plasma. The excited plasma thereupon etches wafer 130 on ceramic ESC stage 131.
During the etching process, the ceramic of dome 120 is etched at the points on the inside surface of ceramic dome 120 that correspond to coil 121 as shown in FIG. 2B, while conversely, deposition 126 adheres to the points that correspond to positions where coil 121 is not present.
After the etching process is completed, first high-frequency power supply 123 and second high-frequency power supply 124 are halted and the supply of etching gas is stopped. When the etching process has been completed, wafer 130 is removed by way of gate 111 of etching chamber 110.
However, the above-described inductively coupled plasma dry etching device of the prior art has the following problems.
First, a reaction product adheres as deposition 126 to the points on the inside surface of ceramic dome 120 that correspond to positions where coil 121 is not present. If the wafer processing continues without addressing this issue, deposition 126 tends to peel off and produce particles on the wafer. As a result, not only must the interior of dome 120 be subjected to cleaning at short intervals, but particles tend to be generated, and the device availability rate drops.
Second, there is the problem that as etching of the interior surface of ceramic dome 120 progresses at points that correspond to coil 121, ceramic dome 120 is reduced and the life of dome 120 is shortened.
It is an object of the present invention to provide a dry etching device and dry etching method that tend not to produce particles, and that feature a high device availability rate and a ceramic dome having longer life.
The dry etching device of the present invention is an inductively coupled plasma dry etching device in which etching is carried out by causing an active gas plasma to act on a wafer secured inside an etching chamber under reduced pressure; the dry etching device being provided with: an etching chamber, a plasma generation means, a wafer securing means, an etching gas supply means, and a gas pressure control means. The plasma generation means includes two high-frequency power supplies that can be switched, and two coils for high-frequency power application that are connected to the two high-frequency power supplies. The two coils for high-frequency power application are each arranged in proximity to the other such that turns of each coil lie between turns of the other coil.
The plasma generation means may have a dome, and the two coils for high-frequency power application may be arranged around the outside of the dome in a helical form such that turns of each coil lie between turns of the other coil; or the plasma generation means may have a quartz plate and the two coils for high-frequency power application may be arranged on the outer surface of the quartz plate in a spiral form such that turns of each coil lie between turns of the other coil.
The dry etching method of the present invention is a method for performing dry etching by causing active gas plasma to act on a wafer that is secured inside an etching chamber under reduced pressure. In a dry etching method that employs an inductively coupled plasma dry etching device, etching is carried out by: conveying a wafer into an etching chamber and securing the wafer, introducing an etching gas into the etching chamber, regulating the interior of the etching chamber to a prescribed pressure, supplying high-frequency power from high-frequency power supplies to either of two coils for high-frequency power application belonging to a plasma generation means that are arranged in proximity to each other such that turns of each coil lie between turns of the other coil, and activating the etching gas; and further, switching the two high-frequency power supplies at a prescribed time interval so as to alternately supply high-frequency power to one of the two coils for high-frequency power application that are each connected to a respective power supply.
The interval of switching the high-frequency power supplies may be 1/nth of the time required for a prescribed etching process of one wafer, n being an even number; may be xc2xd the time required for a prescribed etching process of one wafer; or may be the time required for a prescribed etching process of one wafer, the high-frequency power supplies being switched with each exchange of a wafer.
The dry etching device of the present invention is an etching device that employs a plasma source which is an inductively coupled plasma method, includes two inductively coupled coils, and allows high-frequency power to be independently applied to each of the two coils.
High-frequency power is alternately applied to two coils that are arranged in helical or spiral form such that a turn of each coil lies between turns of the other coil, thereby causing etching and accumulation of deposition to occur alternately at points on the rear surface of the dome or quartz plate that correspond to the two coils. As a result, by carrying out the etching process using the two coils for the same amount of time, the amount of accumulation of deposition can be reduced and particles on the wafers that are caused by peeling off of the deposition can be suppressed despite continuous and repeated etching of a large number of wafers.
The above and other objects, features, and advantages of the present invention will become apparent from the following description based on the accompanying drawings which illustrate examples of preferred embodiments of the present invention.